Film casting of polyethylene terephthalate: Experiments and model comparisons

Cast film extrusions were carried out on polyethylene terephthalate (PET), on a laboratory line. The thermal and the geometrical behavior of the film, in the region from die to chill roll, was studied in different working conditions. The experimental evaluations were performed with an Infrared Thermography (I.R.T.) apparatus. Simplified modeling, describing the non-isothermal behavior of the web, was used to predict temperature, width and thickness of the film in machine direction (MD) as a function of the distance from the die. The above-calculated profiles were compared to those obtained by experimental thermography maps. Measured temperatures resulted different between edge and center of film, i.e. transverse direction (TD) temperature profiles were highlighted. On the contrary, model temperatures are assumed varying only along the machine direction (MD) of web. Thus, from the comparison between experimental and theoretical results, an acceptable agreement was found only in some cases.